Closed reflector provided with incandescent lamp

ABSTRACT

A closed reflector unit provided with an incandescent lamp in which a transparent face plate is secured to the reflector housing by means of an adhesive. The reflector accommodates a drying agent.

United States Patent 1191 Boekkooi et a1.

14s] May 7,1974

CLOSED REFLECTOR PROVIDED WITH INCANDESCENT LAMP Inventors: Anton Boekkooi; Willem Westerveld, both of Emmasingel, Eindhoven, Netherlands Assignee: U.S. Philips Corporation, New

York, NY.

Filed: June 16, 1972 Appl. No.: 263,415

Foreign Application Priority Data June 21, 1971 Netherlands 7108536 US. Cl 313/113, 313/174, 315/108 Int. Cl. HO'lk 1/56, HOlj 5/16 Field of Search ..313/111, 112,113,174,

References Cited UNITED STATES PATENTS Cooper et a1. 313/111 X Beuvens et a1,.,.. 313/178 Milton 313/174 X Plagge et a1. 313/112 X Witteman 313/174 Bader 313/174 Plagge 313/113 Flage 313/113 Primary Examiner-A1fred L. Brody Attorney, Agent, or Firm--Frank R. Trifari ABSTRACT A closed reflector unit provided with an incandescent lamp in which a transparent face plate is secured to the reflector housing by means of an adhesive. The reflector accommodates a drying agent.

4 Claims, 1 Drawing Figure Theinvention relates to a closed reflector unit provided with an incandescent lamp, comprising a reflec tor housing accommodating the incandescent lamp and a transparent face plate which is secured to the reflector housing by means of an adhesive.

Such constructions are known per se. However, up till now there have been unsuccessful attempts to find an adhesive with which a water-vapourtight connection between face plate and reflector housing can be obtained throughout the period of use of the construction. Consequently, such a construction has not yet been introduced for, for example, headlights of motorcars. When using constructions which are not watervapourtight it is possible that water vapor diffused to the inside at low temperatures may condense on the wallof the reflector housing. The reflecting coating on the wall of the reflector housing is, however, generally poorly resistant to water in a liquid state.

reflector housing and the face plate accommodates a' drying agent over which the water vapour pressure at. the highest operating temperatureawhich may occur in this space is lower than or approximately corresponds to the water vapour pressure at C.

The result of this step is that upon cooling, condensation, if it occurs, can only occur in the form of ice. In fact, it has been found that generally reflecting coatings which'are provided on the wall of the reflector housing and particularly vapour-deposited metal coatings are not resistant to water in a liquid state, but are resistant to ice. v

For the object envisaged by the invention the socalled molecular sieves are particularly suitable as drying agents. Examples are the synthetic zeolites as are marketed by the Firm of Union Carbide. Dew points of less than 0C can readily be realised with these materials. The drying agent may be provided at a comparatively arbitrary area within the space enclosed by the reflector housing and the transparent face plate. It is evident that the temperature occurring locally during use is to be taken into account when selecting this area. It is advantageous to provide the drying agent at the area which is coolest during use. Furthermore it is desirable to provide the drying agent in such a manner that loss of light does'not occur. The drying agent is therefore preferably provided as closely as possible to the rim of the reflector housing where it is secured to the face plate by means of the adhesive.

The quantity of the drying agent to be provided is calculated in such a manner that the desired effect is achieved in any case during the period of use of the incandescent lamp. Their great water-absorbing capacity render molecular sieves very suitable for the envisaged object.

The invention will now be further described with'reference to the drawing.

The FIGURE diagrammatically shows in a crosssection a reflector unit comprising; a reflector housing 1 consisting of, for example, steel whose inner side is provided with a reflecting coating of aluminum, a transparent face plate 2, for example, of glass and a halogen incandescent lamp 4 which is secured to a rear plate. 3. The rear plate 3 and the'transparent face plate 2 are secured together with the aidof an adhesive, for example, a cold-setting epoxy resin (5 and 6).

A ridge 7 accommodating the drying agent (Molecular Sieve type 4A of the firm Union Carbide) is provided in the reflector housing near the edge. 2

For a period of use of 3 years of the incandescent lamp and for an internal volume of the reflector unit of 1,000 cubic cm it is found that in the presence of 0.5 g. of the said drying agent there is not condensation of water in a. liquid form during the lifetime of the incandescent lamp, not even in case of extreme temperature fluctuations in a humid climate.

What is claimed is:

1. A closed reflector unit, comprising: a reflector housing. accommodating a closed incandescent lamp and a transparent face plate which is secured to the reflector housing by means of an adhesive, said housing and the transparent face plate enclosing a space which accommodates a drying agent over which the water vapour pressure at the highest operating temperature which may occur in said space is lower thanor approximately corresponds to the water vapour pressure at 0C.

2. A closed reflector unit as claimed in claim 1 3. A closed reflector unit as claimed in claim I wherein the drying agent is provided in the vicinity of that edge of the reflector housing which is connected to the transparent face plate.

4. A closed reflector unit comprising:

a housing having a reflective internal surface, said housing being open at one end;

a closed incandescent lamp positioned within the housing; a

a transparent face plate which is secured to the reflector housing at the open end of the housing by means of an adhesive, said housing and faceplate enclosing a space therebetween; and

. a drying agent positioned within said space over which agent the. water vapour pressure at the highest operating temperature which may occurin said space is lower than or approximately equals the water vapour pressure at 0C, whereby condensation of water vapour in liquid form upon the reflective internal surface of the housing is avoided. 

1. A closed reflector unit, comprising: a reflector housing accommodating a closed incandescent lamp and a transparent face plate which is secured to the reflector housing by means of an adhesive, said housing and the transparent face plate enclosing a space which accommodates a drying agent over which the water vapour pressure at the highest operating temperature which may occur in said space is lower than or approximately corresponds to the water vapour pressure at 0*C.
 2. A closed reflector unit as claimed in claim 1 wherein the unit comprises a molecular sieve material as a drying agent.
 3. A closed reflector unit as claimed in claim 1 wherein the drying agent is provided in the vicinity of that edge of the reflector housing which is connected to the transparent face plate.
 4. A closed reflector unit comprising: a housing having a reflective internal surface, said housing being open at one end; a closed incandescent lamp positioned within the housing; a transparent face plate which is secured to the reflector housing at the open end of the housing by means of an adhesive, said housing and faceplate enclosing a space therebetween; and a drying agent positioned within said space over which agent the water vapour pressure at the highest operating temperature which may occur in said space is lower than or approximately equals the water vapour pressure at 0*C, whereby condensation of water vapour in liquid form upon the reflective internal surface of the housing is avoided. 